Conventional pneumatic tires are designed to perform for relatively long periods of time. In many cases, automobile tires are now expected to have a useful service life of 30,000, 50,000 or 70,000 miles. However, even long-life pneumatic tires are subject to air pressure losses due to puncture by nails and other sharp objects, temperature changes, and/or diffusion of air through the tire itself.
Since air diffusion reduces tire pressure over time, the pneumatic tires may repeatedly become underinflated. Accordingly, drivers must in turn repeatedly act to maintain recommended air pressures in the vehicle tires to avoid reduced fuel economy, tire life, and/or vehicle braking and handling performance. Tire pressure monitoring systems (TPMS) are automated systems that have been proposed to warn drivers when the air pressure in the vehicle tires is significantly low. Such systems, however, remain dependent upon a driver taking remedial action, when warned, to re-inflate a tire to the recommended pressure. It had thus been desirable in the prior art to incorporate an air maintenance feature within a pneumatic tire that would maintain a predetermined or recommended air pressure without requiring driver intervention.
To this end, air maintenance tire (AMT) systems have been developed. An AMT system typically includes one or more pumps or pumping assemblies that act to increase the air pressure in the vehicle tires as needed. An example of one such system is a valve stem-based air maintenance tire system described in U.S. Pat. No. 8,381,784, which is owned by the same Assignee as the present invention, that is, The Goodyear Tire & Rubber Company.
In such AMT systems, and particularly valve stem-based AMT systems, an annular air tube is disposed in a groove formed in a sidewall of the tire and is sequentially flattened or squeezed by the tire footprint as the tire rotates, which directs air to a valve housing. The valve housing is disposed within a wheel rim and is fluidly connected to a tire valve stem, which in turn is in fluid communication with the tire cavity. To enable the fluid communication of air from the annular air tube to the valve housing, one or more connecting tubes extend between the annular air tube and the valve housing.
In order to optimize the operation of such a valve stem-based AMT system, it is desirable to optimize the pumping ability of the annular air tube. Therefore, it is desirable to provide a tire formed with features that enable such optimization of the pumping ability of the air tube.